A few years ago the answer was a flat no: batteries existed to store solar, and without panels the numbers didn’t work. Cheap overnight tariffs changed that. Today a battery-only installation can genuinely pay for itself, provided your usage fits the pattern.
The arbitrage principle
Time-of-use tariffs sell electricity cheaply overnight, sometimes at a quarter of the daytime rate, because national demand is low while the grid keeps running. A home battery buys at the low rate, stores it, and powers your home through the expensive hours. You keep living exactly as before; only the price you pay changes.
Work the numbers on a typical home using 10kWh across the day at around 28p per kWh. Shift that consumption to a 9p overnight rate and you save roughly 19p per kWh, close to £700 a year, before the battery has done anything clever. Systems like SigenStor with native dynamic-tariff support can improve on that by buying on the cheapest half-hours of agile pricing.
When battery-only makes sense
- Your roof can’t take panels. Listed buildings, heavy shading, north-facing terraces, or simply no suitable roof area.
- You’re home in the evenings. The more of your usage that falls in peak hours, the more the arbitrage saves.
- You have, or can get, a time-of-use tariff. The whole case rests on the gap between cheap and expensive rates.
- You want backup. Add a gateway and the same battery keeps your home, or the circuits you choose, running through power cuts.
When it doesn’t
If you’re out all day and your consumption is small, the arbitrage has little to work on. And if your roof is good, solar plus battery beats battery-only in almost every case: generation stacks with arbitrage, and the system earns in daylight as well as overnight. That’s why we model both options before recommending either.
Want the numbers for your home? Two minutes with our savings calculator gives you a first estimate, and a free consultation gives you the real ones.
This guide is general information, not advice for your specific property. Every Powergy proposal is modelled on your actual roof, usage and tariff. Figures reflect typical UK conditions at the time of writing.